Sulfur-containing organosilicon compounds are useful as a component for blending in silica-reinforced rubber composition used for the production of a tire. The silica-reinforced tire exhibits improved properties, and in particular, improved abrasion resistance, rolling resistance, and wet grip in automobile applications. These properties are closely related to the improvement of the low fuel consumption property of the tire, and active studies have been carried out.
As described above, increase in the silica content in the rubber composition is required for the realization of the low fuel consumption. However, silica-reinforced rubber compositions suffered from high viscosity before the vulcanization, and this resulted in the need of multiple-step kneading and low workability despite the decrease of the rolling resistance and the increase of the wet grip of the tire. Accordingly, a rubber composition prepared by simply blending an inorganic filler such as silica suffered from the problems of insufficient filler dispersion which resulted in the drastic loss of strength at breakage and abrasion resistance. In view of such situation, a sulfur-containing organosilicon compound had been required for improving the dispersibility of the inorganic filler in the rubber and realizing chemical bonding of the filler with the rubber matrix.
Examples of the known effective sulfur-containing organosilicon compound include a compound containing an alkoxysilyl group and a polysulfide silyl group in the molecule, for example, bis-triethoxysilylpropyl tetrasulfide and bis-triethoxysilylpropyl disulfide.
In addition to the organosilicon compound having a polysulfide group, also known are thioester-type organosilicon compound containing capped mercapto group which is advantageous for silica dispersion; and sulfur-containing organosilicon compound having an aminoalcohol compound transesterified to the hydrolyzable silyl group moiety which is advantageous in view of the affinity for silica by hydrogen bond.
However, a rubber composition for tire which has realized the desired low fuel consumption has not yet been realized by the use of such sulfur-containing organosilicon compounds. Examples of the remaining problems include higher cost compared to the sulfide-type compound and insufficient productivity due to the complicated production method.
The following literatures disclose prior art technologies relating to the present invention.